Lamp base



FIG. 1 is a perspective view of the lamp base showing my new design;

FIG. 2 is a plan view of the lamp base;

FIG. 3 is an enlarged view of the blocked area identified as 3in FIG. 2;

FIG. 4 is a front elevational view of the lamp base; and

FIG. 5 is a side elevational view of the lamp base. 

The ornamental design for a lamp base, as shown and described. 